The present invention refers to a device for satinizing and embossing packaging foils, comprising a first, a second, and a third embossing roll, the first embossing roll being in rolling contact with each of the second or third embossing rolls and the packaging foil being capable of being passed under pressure between the first and the second and between the first and the third embossing rolls in order to produce a satin-finish and a pattern, the first embossing roll having a tooth array arranged in a basic grid and composed of homogenously arranged individual teeth, and the other two embossing rolls having a surface structure that differs from that of the first embossing roll.
However, it is also possible to use a device for satinizing and embossing packaging foils, comprising a first and a second embossing roll, the two embossing rolls being in rolling contact with one another and the packaging foil being capable of being passed under pressure between the first and the second embossing rolls in order to produce a satin-finish and a pattern, the first embossing roll having a tooth array arranged in a basic grid and composed of homogenously arranged individual teeth, and the other embossing roll having a surface structure that differs from that of the first embossing roll.
Devices of this kind are known from U.S. Pat. No. 7,147,453 to the applicant of the present invention. This patent is a further development of the device according to U.S. Pat. No. 6,715,411 to the same applicant. The two devices defined therein have in common that the paper web first passes through a first roll pair and then through a second roll pair, the application of three rolls allowing to reduce the contact pressure and to achieve an improved breaking of the paper component of the foil.
The surface structures of the embossing rolls, i.e. the arrangements of teeth, circular ridges, or longitudinal ridges on the known rolls, break the paper symmetrically, whereby, as compared to the previously known state of the art, a more homogenous breaking of the fibers in two directions and finer embossing patterns can be achieved, wrinkling in the logo area is avoided, a reduced tendency to tubing and curling is observed, and a good fold capacity, or a so-called dead fold capacity, can be achieved.
Recently, however, further problems have been encountered with foils on a paper substrate. Some of these problem areas resulting from the various new paper properties are indicated below:
a) An influential factor that is difficult to control is the inconsistency regarding the composition of the foil, or inner liner, as it is called in the cigarette industry, the difficulties residing in the fact that the diversity of commercially available inner liner papers is continuously increasing without any standardization tendencies being apparent. This means that depending on the region or the requirements from the marketing sector, papers having a specific surface weight of 30 g/m2 to 80 g/m2 are being used which are metallized, aluminum coated or surface-treated, e.g. by printing, to obtain a metal-like surface. In the application of so-called shadow embossings, see e.g. U.S. Pat. No. 7,036,347 to the applicant of the present invention, very fine structures are produced which have to be embossed with constant quality independently of the material.
b) The mechanical properties of the foils are largely determined by the pulp fibers that are used, by their morphological properties, and the way they are processed. Outwardly similar foils may therefore strongly differ in their mechanical behavior. For these reasons, it is desirable to achieve good results with inner liners of poor quality.
c) For the industrial embossing of the different foils it is therefore desirable to become more independent from their large sensitivity range.
d) Another, economical challenge consists in embossing foils of different compositions in such a manner that they hardly differ from each other optically any more when contemplating similarly embossed marks. In the current state of the art, depending on the composition of the foil, the same embossing patterns, both in logos and in shadow embossings, may look very different to the eye.